Iron and an iron alloy (the iron alloy in the present description is the concept including steel as a matter of course and the steel also includes stainless steel) have high strength and rigidity and are widely used as industrial materials. An iron alloy article in which a resin is bonded to at least a portion of a surface of an iron alloy base ensures excellent rigidity, which cannot be obtained by a resin molded article alone, using the iron alloy base, and also enables a complicated shape and aesthetics, which cannot be achieved by an iron alloy alone, using the resin. Therefore, the iron alloy article is used in various fields including above applications.
There has hitherto been used a method in which an iron alloy base is provided with notches or perforations in advance and, in the case of performing in-mold molding of the iron alloy base by injection molding using a resin, the resin enters into these portions thereby fixing the resin to the iron alloy base.
However, this method has a problem that it is necessary to ensure the place where notches or perforations are provided, resulting in large restriction on design, and a problem that a bonding force is not exerted between a resin and a base except for the notch or perforation portion and thus a gap may be formed between the base and the resin. Therefore, according to this method, since the iron alloy base and the resin are not completely integrated, the resin portion, which is likely to be deformed when deforming stress is applied, easily undergoes deformation, thus making it impossible to use of rigidity of the iron alloy base. Therefore, it is sometimes impossible to ensure rigidity, which cannot be obtained by the resin molded article alone, using the iron alloy base.
Thus, there has been proposed, as a method which does not require notches or perforations and can exerting a bonding force over the entire bonding surface between a resin and a base, a method of bonding a rubber and a metal, characterized by bringing an acidic surface treatment agent into contact with a surface of a metallic material to form a coating layer on the surface of the metallic material, peeling a portion or all of the coating layer, coating a resin composition containing a silane coupling agent thereon, drying the resin composition and coating an aqueous adhesive primer for rubber/metal and an aqueous adhesive for rubber/metal thereon, followed by drying and further vulcanization bonding of a rubber material (Patent Document 1).
Furthermore, there have been proposed a method characterized by roughening a surface of an iron alloy material of a lead frame material through dull roll rolling or etching to form a roughened surface having fine unevenness so as to improve tight adhesion between a lead frame for semiconductor package and a sealing material, adjusting the arithmetic mean roughness within a range from 0.05 to 0.8 μm and also adjusting the surface area substitution value within a range from 1.005 to 1.08, and molding the sealing material composed of a thermosetting resin such as an epoxy resin thereon (Patent Document 2), and a method characterized by subjecting a surface of metal components to a surface treatment with triazinethiols in advance, or performing microetching using an etching solution such as an aqueous permanganic acid solution having strong oxidizability so as to adjust surface roughness Ra within a range from 1 to 10 μm, or forming an oxide layer on a surface using an oxidizing agent, in order to increase an adhesive strength in the case of in-mold molding of a metal terminal of a connector and a holding portion made of a resin, and molding an integrating a nylon resin containing a polyfunctional monomer, followed by crosslinking and a heat treatment at 100° C. or higher of the nylon resin through irradiation with radiation (Patent Document 3).    Patent Document 1; JP 2001-260235A    Patent Document 2; JP H10-270629A    Patent Document 3; JP 2001-047462A